The art of staging presentations that incorporate optical illusions has been practiced for many years. One of the most popular illusions is created through use of projectors and screens and results in apparent three-dimensional images that a viewing audience sees on-stage during a show or presentation.
These prior art illusion systems can be generally categorized as follows: projections onto gauze or other transparent surfaces; projections on live smoke; three-dimensional film technique; and multiple Blue Room techniques. The categories of systems are discussed in substantial detail in U.S. Pat. No. 4,805,985 to Rogers. The discussion includes detailed explanations of the various different Blue Room techniques.
More recently, changes in technology have allowed for more sophisticated systems with computerized lighting coordinated with projectors. There has even been teaching of combining projection systems with object tracking devices to tie live performances in with the projection system. These types of techniques are described in U.S. Pat. Nos. 5,685,625 and 5,528,425 to Beaver.
Drawbacks with existing technologies noted above include the possible logistic nightmare of a projection system. A screen and projector combination typically requires substantial space between a screen and projector. The combination is also a concern with respect to the registration of the projector itself in relation to the screen. The process of projection convergence and screen alignment is time consuming and requires a skilled technician. In any event, when performing on-stage and using two screens like in Beaver, there must be space between the rear projector and the rear screen as well as space between the second projector and the overhead screen. In smaller auditoriums or meeting places, it is very difficult to try to stage these systems such as, for instance, the Beaver system. Space limitations may require a substantial reduction in the size of the effects area that can be created.
In addition to the foregoing, there are fundamental limitations to projection systems generally. First, the use of lighting on-stage to illuminate a person or actor can wash out the images being projected on the various screens, particularly a back screen. Also, in order to achieve some effects, the screens are movable. Moving screens will require moving projectors and the resulting logistical drawbacks coordinating the projector/screen movement.
Another problem with live presentations is coordinating a live performance with images shown on various screens. The Beaver reference discloses object tracking devices to try to solve this problem, but known tracking systems may not always be reliable. Known tracking systems may also be subject to interference from adjacent metal structures (especially if moving) and from adjacent electrical equipment systems. Tracking systems are also very expensive and difficult to integrate with multiple graphics, video, lighting and other equipment system control software. Rather than using a tracking device, an actor giving a live performance usually must look at an off-stage monitor to see what the audience sees and react accordingly. These side glances can take away from the overall visual effect of a performance. In other words, it is difficult for an actor to see the same composite imagery as the audience, because the actor is in the middle of the composite.